NEUROPROTECTIVE EFFECTS OF CARVEDILOL, A NEW ANTIHYPERTENSIVE AGENT, IN CULTURED RAT CEREBELLAR NEURONS AND IN GERBIL GLOBAL BRAIN ISCHEMIA

Background and Purpose: Free radical generation mediates part of the ischemic neuronal damage caused by the excitatory amino acid glutamate. Carvedilol, a novel multiple-action antihypertensive agent, has been shown to scavenge free radicals and inhibit lipid peroxidation in swine heart and rat brain homogenates. Therefore, we studied the neuroprotective effect of carvedilol on cultured cerebellar neurons and on CA1 hippocampal neurons of gerbils exposed to brain ischemia. Methods: Neuroprotective mechanisms were studied using an in vitro ischemia model of cultured rat cerebellar granule cell neurons exposed to either glutamate or oxygen free radical-generating systems. Prevention of lipid peroxidation by carvedilol was studied by measuring the formation of thiobarbituric acid-reactive substance. Gerbil CA1 neuron survival was examined by direct neuronal count 7 days after 6 minutes of global ischemia with reperfusion. Results: Carvedilol protected cultured neurons in a dose-dependent manner against glutamate-mediated excitotoxicity (inhibitory concentration [IC50] = 1.1 muM) as well as against a 20-minute oxidative challenge (IC50=5 muM). The IC50 against the oxidative challenge was lowered to 1.3 muM by growing neurons for 24 hours in the presence of carvedilol. At 10 muM carvedilol inhibited lipid peroxidation 50% and 73% (n=4, p<0.001) in neurons exposed to two different free radical-generating systems. Neuroprotection of 52% (n=22, p=0.009 versus vehicle) of gerbil CA1 hippocampal neurons was achieved by pretreatment and posttreatment with subcutaneous injection of 3 mg/kg carvedilol twice a day for 4 and 3 days, respectively. Conclusions: Carvedilol provided neuroprotection in both in vitro and in vivo models of neuroinjury, where oxygen radicals are likely to play an important role. Therefore, carvedilol may reduce the risk of cerebral ischemia and stroke by virtue of both its antihypertensive action and its antioxidative properties.